Method of preparing aluminum sulfate

ABSTRACT

A method of processing a non-virgin sulfuric acid solution for the preparation of aluminum sulfate comprises the steps of combining a sulfuric acid solution having less than about 90% sulfuric acid with a water solution to form a mixed solution of no less than about 10% sulfuric acid. An alumina-containing compound such as aluminum hydroxide or aluminum bauxite is then added to the mixed solution to form aluminum sulfate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent Ser. No.16/676,060, which is a continuation of U.S. patent application Ser. No.16/035,189 filed Jul. 13, 2018, now U.S. Pat. No. 10,501,330, hereinincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates generally to methods of preparing aluminumsulfate; and more specifically, to methods of preparing aluminum sulfateusing sulfuric acid.

History of Related Art

Sulfuric acid is a basic raw material used in a wide variety ofmanufacturing processes and industries including, for example, theproduction of phosphate fertilizers, paper, inorganic pigment, andindustrial organic chemicals. In the production of liquid aluminumsulfate, virgin or highly concentrated sulfuric acid (i.e., 93-98%) istypically first reacted with aluminum hydroxide and heated prior todilution with water and cooling steps to obtain liquid aluminum sulfate.2Al(OH)₃+3H₂SO₄→Al₂(SO₄)₃+6H2O

The use of sulfuric acid solutions other than virgin sulfuric acid inthe above method provides for incorporation of only small amounts (≤10%)of sulfuric acid solutions having concentrations less than 93%.

SUMMARY

There is a need for a method that provides for use of a substantialamount of a sulfuric acid solution other than virgin sulfuric acid forthe production of aluminum sulfate.

Below is a simplified summary of this disclosure meant to provide abasic understanding of the method(s) described herein. This is not anexhaustive overview and is not intended to identify key or criticalelements or to delineate the scope of the description. Its sole purposeis to present some concepts in a simplified form as a prelude to themore detailed description below.

In one aspect, the present disclosure relates to a method of processinga sulfuric acid solution in the preparation of liquid aluminum sulfate,the method comprising the steps of combining a water solution with asulfuric acid solution comprising no more than about 90% sulfuric acid;mixing the water solution and the sulfuric acid solution to form a mixedsolution comprising a concentration of sulfuric acid; and adding analumina-containing compound to the mixed solution to form aluminumsulfate.

In certain embodiments, the water solution may comprise between about10% and about 100% water. In some embodiments, prior to the combiningstep, the sulfuric acid solution comprises no more than about 75%sulfuric acid. In some embodiments, prior to the combining step, thesulfuric acid consists of sulfuric acid, hydrogen peroxide, and water.In any embodiment described herein, the concentration of the sulfuricacid of the mixed solution is between about 10% and about 85%. In someembodiments, the concentration of the sulfuric acid of the mixedsolution is between about 50% and about 85%. In some embodiments, themixing step comprises a step of adding at least one of virgin sulfuricacid and water to form the concentration of sulfuric acid in the mixedsolution. In any embodiment, the alumina-containing compound comprisesone of aluminum hydroxide and aluminum bauxite.

In some embodiments, the mixing step is performed continuouslythroughout the combining, mixing, and adding steps. In some embodiments,the adding step is performed at a temperature of at least about 150° F.In any embodiment, the method further comprises a step of maintaining apH of the heated solution to less than about 2.0. In some embodiments,the method comprises a step of adding water to the aluminum sulfate toobtain a specific gravity of less than about 1.36. In some embodiments,the method may comprise a step of cooling the aluminum sulfate. In someembodiments, the method may comprise a step of filtering the aluminumsulfate. In some embodiments, the method comprises the step of adding asubsequent sulfuric acid solution having less than 90% sulfuric acid tothe aluminum sulfate to form acidified aluminum sulfate.

In any embodiment, at least the mixing and the adding steps may beperformed in a vessel. In some embodiments, the method further comprisesremoving the aluminum sulfate from the vessel and repeating thecombining, mixing, and adding steps in the vessel to form additionalaluminum sulfate. In embodiments forming additional aluminum sulfate inthe vessel, the combining step comprises a subsequent water solution,the subsequent water solution comprising between about 10% to about 100%water. In embodiments forming additional aluminum sulfate, the mixingstep may comprise a subsequent mixed solution, the concentration ofsulfuric acid of the subsequent mixed solution ranging from betweenabout 10% to about 85%.

Other aspects, embodiments, and features of this disclosure will becomeapparent in the following written description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asfurther objectives and advantages thereof, will be best understood byreference to the following detailed description of illustrativeembodiments when read in conjunction with the accompanying drawings,wherein:

FIG. 1 is a flowchart of one embodiment of the method described herein.

FIG. 2A depicts one embodiment of a mixing device and agitator bladeused for mixing.

FIG. 2B depicts a side view of the embodiment shown in FIG. 2 a.

FIG. 2C depicts a top view of the embodiment shown in FIG. 2 a.

FIG. 3 depicts one embodiment of a system described herein.

DETAILED DESCRIPTION

Several embodiments of Applicant's invention will now be described withreference to the drawings. Unless otherwise noted, like elements will beidentified by identical numbers throughout all figures. The inventionillustratively disclosed herein suitably may be practiced in the absenceof any element which is not specifically disclosed herein.

FIG. 1 is a perspective view of one embodiment of a method describedherein for processing a sulfuric acid solution for the preparation ofliquid aluminum sulfate. A water solution and a sulfuric acid solutionare first combined 10 in a mixing device or vessel. In some embodiments,the water solution comprises at least about 10% water. In someembodiments, the water solution comprises at least about 25% water. Insome embodiments, the water solution comprises at least about 50% water.Water, as used herein and described throughout this method, generallyrefers to pure, deionized and/or tap water, whether hard water or softwater. In some embodiments, the water may comprise room or ambienttemperatures of between about 60-75° F., for example. However, wateroutside these temperatures may also be used. In some embodiments,suitable water is potable.

In some embodiments, the water solution comprises between about 10% andabout 100% water. In some embodiments, the water solution comprisesbetween about 15% and about 100% water. In some embodiments, the watersolution comprises between about 20% and about 98% water. In someembodiments, the water solution comprises between about 25% and about95% water. In some embodiments, the water solution comprises betweenabout 50% and about 90% water. In some embodiments, the water solutionsubstantially comprises water. In some embodiments, the water solutionconsists of water. In some embodiments, the method is repeated such thata small amount of the alumina-containing compound from previous batchpreparations is present during a combining step, further describedbelow. In some embodiments, the water solution comprises no more thanabout 5% alumina-containing compound. In some embodiments, the watersolution comprises no more than about 2% alumina-containing compound.

The sulfuric acid solution combined with water is a non-virgin sulfuricacid solution; that is, a sulfuric acid solution comprising no more than90% sulfuric acid. In some embodiments, prior the combining step 10, thesulfuric acid solution comprises no more than about 80% sulfuric acid.In some embodiments, prior the combining step 10, the sulfuric acidsolution comprises no more than about 75% sulfuric acid. In someembodiments, the sulfuric acid solution comprises no more than about 65%sulfuric acid. In some embodiments, the sulfuric acid solution comprisesno more than about 60% sulfuric acid. In some embodiments, the sulfuricacid solution comprises between about 60% and about 75% sulfuric acid.In some embodiments, the sulfuric acid solution comprises between about65% and about 70% sulfuric acid. In some embodiments, the sulfuric acidsolution comprises between about 60% and about 70% sulfuric acid.

Generally, the sulfuric acid solution to be combined with the water inthe combining step 10 comprises sulfuric acid and water. In certainembodiments, prior to the combining step 10, the sulfuric acid solutionalso comprises hydrogen peroxide. Hydrogen peroxide may be present in anamount up to about 20% by weight of the sulfuric acid solution prior tothe combining step 10. In some embodiments, the sulfuric acid solutioncomprises at least 0.1% to about 6% hydrogen peroxide. In someembodiments, the sulfuric acid solution comprises at least 0.5% to about6% hydrogen peroxide. In some embodiments, the sulfuric acid solutioncomprises at least 1.0% to about 6% hydrogen peroxide. In someembodiments, the sulfuric acid solution comprises between about 2% toabout 4% hydrogen peroxide. In some embodiments, the sulfuric acidsolution comprises between about 3% to about 4% hydrogen peroxide. Insome embodiments, the sulfuric acid solution consists of sulfuric acid,hydrogen peroxide, and water. Thus, in certain embodiments, the sulfuricacid solution to be combined in the step 10 is free of metal. In allembodiments described herein, the aluminum sulfate produced using themethod described herein is free of nitric acid, and all components andsteps are free of nitric acid. In some embodiments, the sulfuric acidsolution comprises between about 10% to about 50% water. In someembodiments, the sulfuric acid solution comprises between about 15% toabout 45% water. In certain embodiments, the sulfuric acid solutioncomprises between about 19% to about 38% water. Suitable sulfuric acidsolutions for the combining step 10 may be prepared or obtained, forexample, as sulfuric acid waste from any number of industrial processes.

Returning to the discussion of FIG. 1, in certain embodiments, thecombining step 10 comprises simultaneous adding of the sulfuric acidsolution and the water into a single mixing device or vessel, anembodiment of which will be further described below. In otherembodiments, the combining step may be performed by sequentially addingwater and the sulfuric acid solution, in no particular order. In suchembodiments, the combining step may further comprise alternately orintermittently adding water and the sulfuric acid solution any number oftimes after adding a portion of the sulfuric acid solution to the water.

With reference to FIG. 1, following the combining step 10, the methodcomprises the step of mixing 20 the water and the sulfuric acid solutionto form a mixed solution comprising a concentration of sulfuric acid ofbetween about 10% and about 85%. In certain embodiments, the mixedsolution comprises a concentration of sulfuric acid of between about 50%to about 85%. In certain embodiments, the mixed solution comprises aconcentration of sulfuric acid of between about 10% and about 50%. Incertain embodiments, the mixed solution comprises a concentration ofsulfuric acid of between about 10% and about 75%. In certainembodiments, the mixed solution comprises a concentration of sulfuricacid of between about 15% and about 65%. In certain embodiments, themixed solution comprises a concentration of sulfuric acid of betweenabout 55% to about 80%. In certain embodiments, the mixed solutioncomprises a concentration of sulfuric acid of between about 60% to about80%. In certain embodiments, the mixed solution comprises aconcentration of sulfuric acid of between about 10% and 35%. In someembodiments, the mixed solution comprises a concentration of sulfuricacid of between about 15% and about 25%.

In attaining the proper concentration of sulfuric acid in the mixedsolution, the mixing step 20 may further comprise a step of adding atleast one of: virgin sulfuric acid and water as the mix is being stirredby the agitator blades. The term “virgin sulfuric acid,” as used herein,is meant to refer to a sulfuric acid solution comprising a concentrationof sulfuric acid of 90% or more. Adding virgin sulfuric acid helpsincrease the temperature of the mixed solution to about 175° F. in someembodiments, which may speed promotion of the reaction. Such additionsmay take place simultaneously or sequentially in no particular order. Insome embodiments, the sulfuric acid solution may be combined with avirgin sulfuric acid prior to the combining step 10. In certainembodiments, a ratio of about 50:50 virgin and non-virgin sulfuric acid,for example, may be combined with and mixed with the water. However,other embodiments of the sulfuric acid solution and the mixed solutionare free of virgin sulfuric acid and comprise 100% of the non-virginsulfuric acid solution described above.

In certain embodiments, the combining step 10 and the mixing step 20 maybe performed sequentially. In some embodiments, the combining step 10and the mixing step 20 may be performed simultaneously. Some embodimentsmay also comprise intermittent mixing steps to form the mixed solution.

The combining 10 and/or mixing 20 steps may take place for time periodof over 20 to about 60 minutes, in some embodiments, depending on theinitial sulfuric acid concentration of the solution prior to combining10. Mixing 20 should generally be performed at a speed of between about15 rpm to about 50 rpm, depending on timing and concentrations used. Insome embodiments, the mixing is performed at between about 25 rpm andabout 31 rpm. In some embodiments, the mixing step is performed atbetween about 26 rpm to about 30 rpm. In some embodiments, the mixingstep is performed at between about 28 rpm to about 29 rpm. Inadequatemixing produces too much settling on the bottom. Conversely, if toohigh, undesirable waves will result in the mixing vessel. In someembodiments, the mixing step 20 is performed continuously throughout thecombining 10, mixing 20, and adding steps.

FIGS. 2A-2C illustrate one embodiment of a suitable mixing device 100.FIG. 2A is a cross-section view of a vessel or tank 110 of the mixingdevice 100 comprising a rotating shaft 102 within the tank 110, therotating shaft 102 comprising an impeller 104 on an end near the bottomof the tank 110. The impeller comprises a plate 106 and a plurality ofagitator blades 108 extending from the plate 106. For clarity, FIG. 2Adepicts only two of the four blades 108 of the embodiment shown therein.The plate 106 is connected or mounted perpendicular to the rotatingshaft 102. The plate may comprise a hole in its center for the shaft.The shaft 102 may comprise, for example, a diameter of about 2.25 toabout 2.5 inches. By way of example, the plate may comprise a squareshape with each side about 2 feet long and about 2 feet wide. Othershapes may be possible so long as an axial flow of the component(s)within the mixing vessel is accomplished during mixing.

In some embodiments, the impeller comprises an even number of agitatorblades 108. In certain embodiments, the blades are mounted at an angleextending from an upper left to a lower right. The blades 108 may bemounted at an angle of between about 10° to about 80° with respect tothe horizontal axis of the plate 106. In some embodiments, the blades108 are mounted at an angle of between about 20° to about 70°. In someembodiments, the blades 108 are mounted at an angle of between about 30°to about 60°. In some embodiments, an even number of blades 108 aremounted at an angle of about 45° from the upper left to the lower right.

In some embodiments, each corner of the plate 106 may comprise a slot orslit for each blade 108, the slot comprising a length sufficient toengage with a corresponding slot of a blade 108, as best shown in FIG.2c . Each blade 108 may be inserted and welded into a slot at a cornerof the plate 106 via a corresponding slot in the blade 108, thecorresponding slot of the blade 108 located midway between one end of awidth of the blade. While FIG. 2C shows the slots fully extending out toa perimeter of each of the plate and the blade, other fits may bepossible so long as the plate and connected blades form a solid bond.

The distance x from the bottom of the tank 110 to the blades 108 of theimpeller is from about 0.5 times the diameter y of the impeller to about2.0 times the impeller diameter y. In some embodiments, the distance xranges from about 0.67 to 1.3 times the diameter of the impeller. Asshown in the embodiment depicted in FIGS. 2A-2C, four flat rectangularblades 108 are attached to the square plate 106. In some embodiments,each blade 108 comprises an aspect ratio ranging from about 4:3 to about2:1. For example, when a blade 108 comprises a width of about ten inchesand a length of about 20 inches, a corresponding slot on the blade 108is located on the center of the width of the blade, with about 5 incheson either side of the corresponding slot on the blade. The diameter y ofthe impeller 104 is about 0.25 to about 0.5 times the inner diameter zof the tank 110. In some embodiments, the diameter y of the impeller isabout ⅓ of the inner diameter z of the tank 110. The mixing step thusdescribed herein creates an axial flow pattern between the liquids,which pulls fluid from the top center of the tank and down along theshaft 102 towards the center bottom of the tank, as shown in FIG. 2B.The fluid then flows along the bottom toward and then up the outsidewalls. This keeps the corrosive acid from collecting at the top orcoming in direct contact with the walls of the tank, while promoting theformation of aluminum sulfate, as described below. As shown in FIG. 2C,the fluid rotates in a clockwise direction in some embodiments.

Returning to the discussion of FIG. 1, once a mixed solution is formed,an alumina-containing compound is added 30 to the mixing device,initiating the formation of aluminum sulfate. Suitablealumina-containing compound may comprise aluminum hydroxide and aluminumbauxite, for example. In some embodiments, the alumina-containingcompound comprises aluminum hydroxide. In some embodiments, thealumina-containing compound consists of aluminum hydroxide. In someembodiments, the alumina-containing compound comprises aluminum bauxite.In some embodiments, the alumina-containing compound consists ofaluminum bauxite. Other suitable alumina-containing compounds may alsobe possible in some embodiments.

Generally, the adding step 30 is performed in a controlled manner over aperiod of time sufficient to allow the mixed solution to reach atemperature of at least about 175° F., at which point thealumina-containing compound and the mixed solution begin to react toform aluminum sulfate. In some embodiments, the adding step is performedonce the mixed solution reaches a temperature of at least about 150° F.When the adding step is performed, the temperature of the mixed solutionwill further rise forming what is referred to herein as a heatedsolution. In some embodiments the heated solution reaches a temperatureof at least about 175° F. In some embodiments, the heated solutionreaches a temperature of between about 175° F. and about 225° F. In someembodiments, the heated solution reaches a temperature of at least about200° F. In some embodiments, the heated solution reaches a temperatureof between about 200° F. and about 220° F. In some embodiments, theheated solution reaches a temperature of between about 200° F. and about210° F.

The time duration of the adding step may depend on the volume of themixed solution. In some embodiments, the adding step 30 is performed forat least about 2 hours at a feeding rate of between about 150 to about250 lbs/minute. In some embodiments, the adding step 30 comprises a rateof between about 160 and about 220 lbs/minute. In some embodiments, theadding step 30 comprises a rate of between about 170 and about 200lbs/minute. In some embodiments, the adding step is performed forbetween about 2 hours to about 3 hours. Adding 30 may comprisecontinuous feeding in some embodiments. In other embodiments, adding 30may comprise intermittent feeding of the alumina-containing compound tothe mixing device or vessel. A combination of continuous andintermittent feeding is also possible in some embodiments. Further, insome embodiments, where desirable, the adding step may comprise theadding of an amount of the alumina-containing compound sufficient toform acidified aluminum sulfate.

During the adding step 30, mixing step 20 should continue to beperformed, whether simultaneous or intermittently at speeds as recitedabove. When the mixing speed is too high, heat transfer rates mayincrease along the walls, overcooling the solution and preventing itfrom achieving necessary temperatures for the reaction. Similarly, whenspeed is too low, the temperatures are too low, and the desired reactionis not promoted. In some embodiments, after adding 30, the method maycomprise adding virgin sulfuric acid to increase or maintain thetemperature to at least about 175° F. Water can also be added in someembodiments to cool the temperature to below about 225° F. The addingstep 30 may partially overlap the combining 10 and/or mixing steps 20 insome embodiments. In some embodiments, the adding step 30 at leastpartly overlaps the combining step 10. In some embodiments, the addingstep 30 at least partly overlaps the mixing step 20.

Once all the alumina-containing compound has been added 30, thecombination forming a pH of 2.0 or less, the heated solution is thenallowed to react over a time period of at least about 2 hours. Duringthis period, the method further comprises a step of monitoring andmaintaining a pH 40 of the heated solution (i.e., the mixed solutionwith the alumina-containing compound) to ensure a complete reactionbetween the sulfuric acid and the alumina-containing compound. Theheated solution should comprise a pH of between about 1.6 and about 2.0at this time. Thus, if necessary, the method may comprise a step ofadjusting the pH. Adjusting pH may be performed by adding additionalnon-virgin sulfuric acid solution if the pH is too high. If the pH islow, more alumina-containing compound should be added. The specificgravity of the aluminum sulfate is generally about 1.38 after themonitoring step 40. The monitoring step 40 is performed for up to about12 hours. In some embodiments, the monitoring step 40 is performed forless than about 4 hours. In some embodiments, the monitoring step 40 isperformed for between about 2 hours and about 4 hours.

Once the pH is confirmed to be within the correct range, the method mayfurther comprise the step of obtaining a specific gravity 50 of lessthan about 1.4. In some embodiments, once a specific gravity of lessthan about 1.36 is reached, the aluminum sulfate cools and settlesovernight before filtering and/or storing steps. Optionally, step 50 canbe performed by adding water to the aluminum sulfate to obtain thedesired specific gravity. In some embodiments, water is added to obtaina specific gravity of between about 1.3 to about 1.38. In someembodiments, water is added to obtain a specific gravity of betweenabout 1.34 to about 1.36.

Once the proper specific gravity is attained, the aluminum sulfate maybe cooled 60. Cooling 60 may take place overnight, or for at least about10 hours in some embodiments. In some embodiments, a cooling system maybe used such as one including one or more of a cooling jacket, coolingliquid, or cooling air. Cooling 60 also allows the settling of thereacted solution. Cooling and settling may be performed overnight. Insome embodiments, the cooling and setting steps may be performed for atleast about 10 hours. In some embodiments, the cooling and setting stepsmay be performed for at least about 15 hours. After the cooling period60, the aluminum sulfate is subjected to filtering 70, in someembodiments, and may then be stored 80, if desired. During filtering 70,in some embodiments, the aluminum sulfate may comprise the followingphysical properties at about 160° F. to about 180° F.:

Dry Alum in Solution: 48-49% Al₂O₃ 8.0-8.4% Free Al₂O₃ +/−0.025%  TotalIron as Fe₂O₃ <50 ppm Insoluble Matter <0.02% Specific Gravity 1.325 +/−0.003 pH 1.8-2.5 

It should be noted that embodiments comprising or consisting of aluminumbauxite may comprise additional processing steps to minimize the amountof residual solids leftover after the reaction takes place. By way ofexample and without limitation, in such embodiments, the method maycomprise at least one round of additional settling of the reaction,pumping out aluminum sulfate, and the adding of water to recoverleftover aluminum sulfate before any discarding of unrecoverable waste.

The methods described above to form aluminum sulfate further providesfor the production of additional batches of aluminum sulfate in the samevessel. That is, in any of the embodiments of the methods formingaluminum sulfate, at least the mixing and the adding steps may beperformed in a single vessel. After forming at least a first batch ofaluminum sulfate, the method may further comprise the steps of removingformed aluminum sulfate and repeating combining, mixing, and addingsteps in the vessel to form additional aluminum sulfate. Thus, once anamount of aluminum sulfate is produced, the aluminum sulfate may becollected or removed from the vessel and the vessel may again be used toperform one or more of steps of combining, mixing and/or adding, asdescribed above. In certain embodiments, after forming aluminum sulfate,the method comprises the steps of removing the aluminum sulfate from thevessel; combining a subsequent water solution with a subsequent sulfuricacid solution; mixing the subsequent water solution with the subsequentsulfuric acid solution in the vessel to form a subsequent mixedsolution; and adding a subsequent alumina-containing compound to thesubsequent mixed solution to form additional aluminum sulfate.

In some embodiments, the subsequent water solution is the water solutionused in a previous combining step. In some embodiments, the subsequentwater solution may comprise between about 10% to about 100% water. Insome embodiments, the subsequent water solution comprises at least about10% water. In some embodiments, the subsequent water solution comprisesat least about 25% water. In some embodiments, the subsequent watersolution comprises at least about 50% water. In some embodiments, thesubsequent water solution substantially comprises water. In someembodiments, the subsequent water solution comprises between about 15%and about 100% water. In some embodiments, the subsequent water solutioncomprises between about 20% and about 98% water. In some embodiments,the subsequent water solution comprises between about 25% and about 95%water. In some embodiments, the subsequent water solution comprisesbetween about 50% and about 90% water. In some embodiments, thesubsequent water solution consists of water.

In some embodiments, the subsequent sulfuric acid solution is thesulfuric acid solution used in a previous combining step. In someembodiments, the subsequent sulfuric acid solution comprises no morethan 90% sulfuric acid prior to the combining step. In some embodiments,the subsequent sulfuric acid solution comprises no more than about 75%sulfuric acid prior to the combining step. In some embodiments, thesubsequent sulfuric acid solution consists of sulfuric acid, hydrogenperoxide and water prior to the combining step.

As with the mixed solution discussed above, the concentration ofsulfuric acid in the subsequent mixed solution may range from betweenabout 10% to about 85%. In certain embodiments, the sulfuric acid in thesubsequent mixed solution may range from between about 10% to about 75%.In certain embodiments, the sulfuric acid in the subsequent mixedsolution may range from between about 15% to about 65%.

In some embodiments, the subsequent alumina-containing compound is thealumina-containing compound used in a previous adding step. In someembodiments, the subsequent alumina-containing compound comprises one ofaluminum hydroxide and aluminum bauxite. Other sources of analumina-containing compound may also be possible in certain embodiments.

While current methods of producing aluminum sulfate, which first reacthighly concentrated sulfuric acid with aluminum hydroxide, result infaster manufacturing times, it is believed that the method and systemdescribed herein is less volatile and less sensitive to the presence ofa weaker sulfuric acid solution. Thus, the process is more forgiving andallows substantially all the sulfuric acid solution to be sourced from anon-virgin sulfuric acid as described herein. The method describedherein is also not as aggressive as methods using only or substantiallyonly virgin sulfuric acid, as the temperatures of the reactionsdescribed herein increase slowly and are easily maintained at the propertemperatures for the reaction to fully occur, leaving little residualsolids to clean up. In some embodiments, the present method leavessubstantially no (i.e., less than 1%) residual solids in the mixingvessel following the reaction. The method and system described herein istherefore also safer than currently used methods and provides for asimplified, cost effective way of making aluminum sulfate.

In some embodiments, the method described herein is free of anyadditional or external heating devices or systems including, by way ofexample, steam. Thus, the current method may rely entirely uponexothermic reactions and promoting the sulfuric acid and thealumina-containing compound to fully react in forming the aluminumsulfate in certain embodiments. In some embodiments, the methoddescribed herein may comprise an external heating method or source toforce the reaction and formation of the aluminum sulfate.

The method provided herein also provides a source of aluminum sulfatethat can be used in any number of industries. In some embodiments, theabove-described method producing aluminum sulfate may comprise a step ofadding a subsequent sulfuric acid solution having less than 90% sulfuricacid to the aluminum sulfate to form acidified aluminum sulfate. By wayof example, the subsequent sulfuric acid solution may be added in anamount sufficient to produce between about 1% to about 15% free acid byweight when combined with the aluminum sulfate.

FIG. 3 depicts a system of making aluminum sulfate. The system of makingaluminum sulfate described herein comprises at least a first vessel ortank I and a second vessel or tank II in communication with a singlemixing device or vessel 100. At least one of the first tank and thesecond tank is in communication with both a top half of the mixingdevice and a bottom half of the mixing device. By way of example, FIG. 3depicts the first tank I in communication with both the top and bottomhalves of the mixing device 100. The first tank I may comprise orconsist of, for example, the water or a water solution, while the secondtank II may consist of the non-virgin sulfuric acid, described above.Any number of transportation systems used for fluids such as one or morepipes and one or more pumps may be used to allow that each tank be incommunication with the mixing device 100. As described above in relationto FIGS. 2A-2C, the mixing device 100 comprises an inner diameter and ahollow opening having a rotatable shaft within the hollow opening. Therotatable shaft extends into the hollow opening and comprises animpeller near a bottom wall of the mixing device 100. Further details ofthe mixing device and its impeller are described above in relation toFIGS. 2A-2C.

In some embodiments, the system further comprises a third vessel or tankIII in communication with the single mixing vessel 100. In additionalembodiments, the system further comprises a fourth vessel or tank IV.Tanks III and IV are shown in dashed lines in FIG. 3. The third tank IIImay comprise, for example, virgin sulfuric acid for mixing to thedesired concentration and/or for ensuring complete formation of aluminumsulfate after the adding step. Alternatively, the third tank III maycomprise the alumina-containing compound to allow for the adding orfeeding of the alumina-containing compound to the mixed solution withinthe mixing device 100. In some embodiments, a fourth tank IV may be incommunication with the mixing device 100. The fourth tank IV maycomprise, for example, the alumina-containing compound when virginsulfuric acid is desired for use with the system. Similar to the firstand second tanks, either of the third or fourth tank having anadditional liquid, may communicate with the mixing device 100 via a pipeor pumping system suitable for use with liquid. The tank III or IV, whencomprising the alumina-containing compound, is in communication with themixing device 100 via any number of transporting systems suitable forpowder materials, including without limitation a conveyor belt, a screwauger, or a pneumatic pumping system.

The mixing device 100 comprises a rotatable shaft, an example of whichis described above and shown in FIGS. 2A-2C, provides for mixing of thecomponents added to the mixing device 100. The rotatable shaft isfurther in communication with a motor to control mixing speed of themixing device.

In some embodiments, components of one or more of the first tank, secondtank, third tank, and fourth tank may be fed directly into or near thetop of the mixing device 100. In addition, at least one tank is incommunication with or near a bottom half of the mixing device 100. Incertain embodiments, any of the tanks I-IV comprising water may also befed into or near the bottom of the mixing device 100. As shown by way ofexample in FIG. 3, tank I is in communication with both the top half andthe bottom half of the mixing vessel. In this manner, as describedabove, tank I may comprise water, which may be added to the mixingdevice in forming the mixed solution, or to the adding step of themethod to help adjust the temperature of the heated solution in formingthe aluminum sulfate. The mixing device 100 described in detail inrelation to FIGS. 2A-2C, may further be in communication with a filter.As described above, the system of the present disclosure may be free ofany heating devices.

The words and phrases used herein should be understood and interpretedto have a meaning consistent with the understanding of those words andphrases by those skilled in the relevant art. No special definition of aterm or phrase, i.e., a definition that is different from the ordinaryand customary meaning as understood by those skilled in the art, isintended to be implied by consistent usage of the term or phrase herein.To the extent that a term or phrase is intended to have a specialmeaning, i.e., a meaning other than that understood by skilled artisans,such a special definition is expressly set forth in the specification ina definitional manner that directly and unequivocally provides thespecial definition for the term or phrase.

The terms “including,” “comprising,” “having,” and variations thereofmean “including but not limited to,” unless expressly specifiedotherwise, and, therefore, allow the addition of other elements,components, steps, or parameters. The phrase “substantially comprises,”and its variants, excludes additional material elements or componentsbut allows for inclusions of non-material elements or components andtrace impurities. When used in the appended claims, in original andamended form, the term “comprising” is intended to be inclusive oropen-ended and does not exclude any additional, unrecited element,method, step or material. The term “consisting of” is closed andexcludes any element, step or material other than those specified. Asused herein, “up to” includes zero, meaning no amount (i.e, 0%) is addedin some embodiments.

Unless otherwise specified, all percentages, parts and ratios refer topercentage, part, or ratio by weight of the total. For example, apercent or percentage refers to percent by weight, based on the totalweight of the formulation or composition in which the component isincluded. Unless specifically set forth herein, the terms “a”, “an”, and“the” are not limited to one of such elements, but instead mean “atleast one,” unless otherwise specified. The term “about” as used hereinrefers to the precise values as subsequently indicated as well as tovalues that are within statistical variations or measuring inaccuracies.For example, phrases such as “between about X and about Y” or “betweenabout X to about Y” should be interpreted to include X and Y.

The methods disclosed herein may be suitably practiced in the absence ofany element, limitation, or step that is not specifically disclosedherein. Similarly, specific devices described herein may be free of anycomponent not specifically described herein. Concentrations, amounts,and other numerical data may be expressed or presented herein in a rangeformat. It is to be understood that such a range format is used merelyfor convenience and brevity and thus should be interpreted flexibly toinclude not only the numerical values explicitly recited as the limitsof the range, but also to include all the individual numerical values orsub-ranges encompassed within that range as if each numerical value andsub-range is explicitly recited. For example, the range 1 to 10 alsoincorporates reference to all rational numbers within that range (i.e.,1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range ofrational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and3.1 to 4.7) and, therefore, all sub-ranges of all ranges expresslydisclosed herein are hereby expressly disclosed. These are only examplesof what is specifically intended and all possible combinations ofnumerical values between the lowest value and the highest valueenumerated are to be considered to be expressly stated in thisapplication in a similar manner.

While the invention has been particularly shown and described withreference to certain embodiments, it will be understood by those skilledin the art that various changes in form and detail may be made thereinwithout departing from the spirit and scope of the invention.

What is claimed is:
 1. A method of preparing liquid aluminum sulfate,the method comprising the steps of: combining a water solution with asulfuric acid solution comprising no more than 90% sulfuric acid; mixingthe water solution and the sulfuric acid solution to form a mixedsolution comprising a concentration of sulfuric acid; and adding analumina-containing compound to the mixed solution to form aluminumsulfate.
 2. The method of claim 1 wherein the water solution comprisesbetween about 10% and about 100% water.
 3. The method of claim 1 whereinthe sulfuric acid solution comprises no more than about 75% sulfuricacid prior to the combining step.
 4. The method of claim 1 wherein thesulfuric acid solution consists of sulfuric acid, hydrogen peroxide andwater prior to the combining step.
 5. The method of claim 1 wherein theconcentration of sulfuric acid of the mixed solution is between about10% to about 85%.
 6. The method of claim 1 wherein the concentration ofsulfuric acid of the mixed solution is between about 50% to about 85%.7. The method of claim 1 wherein the alumina-containing compoundcomprises one of aluminum hydroxide and aluminum bauxite.
 8. The methodof claim 1 wherein the mixing step is performed continuously throughoutthe combining, mixing, and adding steps.
 9. The method of claim 1wherein the mixing step comprises a step of adding at least one ofvirgin sulfuric acid and water to form the concentration of sulfuricacid in the mixed solution.
 10. The method of claim 1 wherein the addingstep is performed at a temperature of at least about 150° F.
 11. Themethod of claim 1 wherein after the adding step, the mixed solutionfurther increases in temperature forming a heated solution, and themethod further comprises a step of monitoring the pH of the heatedsolution and optionally adjusting the pH to less than about 2.0.
 12. Themethod of claim 1 further comprising the step of adding water to thealuminum sulfate to obtain a specific gravity of less than about 1.36.13. The method of claim 1 further comprising the step of cooling thealuminum sulfate.
 14. The method of claim 1 further comprising the stepof filtering the aluminum sulfate.
 15. The method of claim 1 comprisingthe step of adding a subsequent sulfuric acid solution having less than90% sulfuric acid to the aluminum sulfate to form acidified aluminumsulfate.
 16. The method of claim 1 wherein at least the mixing and theadding steps are performed in a vessel.
 17. The method of claim 16further comprising the steps of removing the aluminum sulfate from thevessel and repeating the combining, mixing, and adding steps in thevessel to form additional aluminum sulfate.
 18. The method of claim 17wherein the combining step comprises a subsequent water solution. 19.The method of claim 18 wherein the subsequent water solution comprisesbetween about 10% to about 100% water.
 20. The method of claim 19wherein the mixing step comprises a subsequent mixed solution.
 21. Themethod of claim 20 wherein the concentration of sulfuric acid in thesubsequent mixed solution is between about 10% and about 85%.